| 摘要 |
<p>Disclosed are a hot-rolled steel sheet, a manufacturing method thereof which can be normalized at low temperatures by controlling alloy elements and process conditions, and a method for manufacturing a steel pipe using the hot-rolled steel sheet. The manufacturing method of the hot-rolled steel sheet according to the present invention comprises the steps of: reheating a slab composed of 0.20-0.35 wt.% of C, 0.15-0.30 wt.% of Si, 1.2-2.0 wt.% of Mn, 0.2-0.3 wt.% of V, 0.02-0.05 wt.% of Al, 0.015 wt.% or less of P, 0.005 wt.% or less of S, 0.002 wt.% or less of Ca, 0.008 wt.% or less of N, and the rest of Fe and inevitable impurities; hot-rolling the reheated slab; and cooling the hot-rolled slab, and coiling the slab at 550-620°C, which is a coiling temperature (CT). [Reference numerals] (AA) START;(BB) END;(S110) Slab reheating (SRT : 1150-1300°C);(S120) Hot-rolling ((FDT : 840-880°C);(S130) Cooling/coiling(CT : 600-660°C)</p> |
